1. Field of the Invention
The present invention relates to a data mirror cluster system and a method for synchronizing data, and particularly to a cluster system and method capable of synchronizing data of multiple servers at high speed.
2. Description of the Related Art
In the data mirror cluster system, the respective nodes are connected to each other using a connecting section such as LAN and the like as an interconnect to synchronize data between nodes.
However, when a protocol such as TCP/IP is used, a software stack for use in the protocol is deep and communication is performed via an I/O device and the like to cause a problem in which latency is increased.
The interconnect used here is a connecting section, which serves as an input/output interface between an operation server and a standby server (multiple standby servers may be possible) that configure the cluster to synchronize data between the operation server and the standby server.
Moreover, the latency indicates a time difference in synchronization between the start of synchronization processing and the end thereof when data of the operation server updated by the operation server is synchronized with the standby server.
In the data mirror cluster system, there is need to update a database of the standby system based on a change in data stored in the database of the operation server as required to obtain synchronization between the operation server and the standby server.
In the case of the system having a large latency, much time is required to perform data synchronization between the operation server and the standby server. Since time intervals in data synchronization are increased, there is a case in which an amount of data to be transferred in one synchronization processing is increased
As a result, when trouble occurs in the operation server to fail over to the standby system, an amount of information to be lost is increased since synchronization with the standby system is not obtained during the trouble, so that merits resulting from combination with the cluster configuration are reduced.
Unexamined Japanese Patent Application KOKAI Publication No. H04-299435 discloses one of synchronization controlling methods in a cluster system. In this cluster system, each of an operation server and a standby server has a different database. This cluster system can perform synchronization in database between the operation server and the standby server in an on-line state. However, in this cluster system, an idea for reducing the latency is not provided.
Unexamined Japanese Patent Application KOKAI Publication No. H08-221289 discloses another improved cluster system configuring method. In this cluster system, each node has a memory address space of the corresponding system and a memory address space of the other system. Moreover, there is a symmetry in a logical structure between the memory address space of the corresponding system and the memory address space of the other system.
However, in this configuration, management of the memory address space of the corresponding system and the memory address space of the other system is complicated. Moreover, an address conversion between the memory address space of the corresponding system and the memory address space of the other system is required.
Unexamined Japanese Patent Application KOKAI Publication No. H11-149388 discloses further another improved cluster system configuring method. In this cluster system, each of an operation server and a standby server has two main storage devices. When data is stored in a first main storage device of one server apparatus, data is transferred to a second main storage device of the other server apparatus to perform synchronization using DMA (Direct Memory Access) transfer.
However, in this configuration, management of memory address spaces of two main storage devices is complicated. Moreover, a DMA controller is required to be initialized at a DMA transfer staring time, so that a bottleneck of latency may occur.
As mentioned above, in the conventional data mirror cluster system, there are problems in that much time is required to perform data synchronization between the operation server and the standby server and management of the memory address spaces is complicated.
The present invention has been made with consideration given to the aforementioned circumstances, and an object of the present invention is to reduce an amount of data failing in mirror synchronization at a trouble occurring time.
Moreover, another object of the present invention is to provide a cluster system with easy control and management and its controlling method.